Crimping or curling of yarns or threads



P. VAN DlJK July 5, 1960 CRIMPING OR CURLING OF YARNS OR THREADS 3 Sheets-Sheet Filed Feb. 29. 1956 INVENTOR fi'eler vanfl zjx A it UL- d ATTORNEY July 5, 1960 P. VAN DIJK GBIMPI NG 0R CURLING OF YARNS OR THREADS 3 Sheets-Sheet 2 Filed Feb. 29, 1956 I I'lllffi'lllIlllllflilill R m N w m Pieier mnfljl I ATTORNEY P. VAN DIJK July 5, 1960 CRIMPING OR CURLING 0F YARNS OR THREADS 3 Sheets-Sheet 3 Filed Feb. 29. 1956 m T N E V m Pz'eler van 1' ATTORNEY United States Patent 2,943,433 r cnnvrruvo on CURLING or YARNS on THREADS Pieter van Dijk, Velp, Netherlands, assignor to. American Enka Corporation, Enka, N.C., a corporation of Delaware Filed Feb. 29, 1956, SenNo. 568,666

Claims priority, application Netherlands Man-4, 1955 9 Claims. (Cl. 57--34) This invention relates to the crimping or curling of thermoplastic yarns or threads and more particularly to improvements in false twisters which impart to the yarn the curl that is made permanent by sequential heating and cooling.

In the preparation of curly yarn of the thermoplastic type the usual procedure is to pass succeeding lengths of running yarn through a false twister and heating and cooling before the false twist is taken out. Since the degree of curl imparted to the yarn is a function of the twist present at the time the curl is set, it is apparent that the speed at which the process can be performed continuously is a function of how fast the false twist can beput in. For example, in a false twister of the type shown in copending application Serial No. 442,166,filed July 8, 1954, in the name of Conrad Joseph Gonsalves, and commonly owned herewith, the hollow spindle of the false twister must rotate at 60,0 00 r.p.m. in order to put in 3000 turns per meter in a yarn running at only 20 meters a minute. Much higher yarn speeds during curling have not been heretofore achieved due to the excessive speed demands which they make on the bearings of the hollow spindle which is inserting the false twist.

In an attempt to solve the bearing problem, it has been proposed to pass succeeding lengths of yarn to be twisted between two belts running in opposite directions. These belts are so run in relation to each other'that the yarn -'is rolled between them producing a large number of turns of false twist from relatively slow belt speeds. On the .other hand, the guiding of the'belts and the yarn at the crossing point is required tobe cr-itically accurate 'and the spacing between them has to-bequite small. Theinistallation is'there'fore theoretically promising but in prao ttice is quite difficult tobuild andmaintain.

'Aceordinglyyit is an objeet ofthe presentinvention to overcome the problems of the prior-art; and to provide "a device of low peripheral speed for impa'rting high twist "to yarns running at-"hi-gh speed while automatically locating the yarn in correct 'r elation' tothe surface whichis imparting false-twist to it.

The false twist device according-to the inventionis characterizedinithat two irotatab'ly mounted. rollers iinlthe formof i hyperboloids are. present. cooperating with each ".otherrandieach witha dn'vingmeans, the -1cr.oss ing :angles -between the axis a'nd the; generatio straight line being the same and "which hyperboloids are so mounted with regard 'to -eaehother thatthe axes thereof make-an angle with each other :which i-sitwice as large as the said crossing angle, the thread supply :and' {discharge devices be ng arranged-ropposite one-of the anglesz'between the two hyperboloid axes so that the yarn path bisects it. V

aIt' has heenr-found asapart of the present invention that ethe'curlsor :crimpproduced: is greatly improved if a :very small diameter tubular cooler is ;u sed,;in order that: the heatin the ramm y be ex tedywnd on re u tin from osci lation of ther miaga stthe -c oler fac -Strang lr en ug tr tch g e o s eet ng "ha e .-fcunr1-to =+be sa is acto y i f yre ternat on-a di boloid 5 at an angle a.

ice

2 result in improved curling as well as the advantages of stretching as a part of a continuous process.

Other objects and advantages of this invention will be apparent from the following detailed description of several embodiments thereof in conjunction with the annexed drawings wherein:

Figure 1 is a geometric drawing illustrating the theoretical steps involved in calculating the curvature of the false twist rollers which will be referred to in the specification as hyperboloids; V

Figure 2 is a schematic view in elevation showing a yarn curling system involving hyperboloid rollers having their surfaces calculated and arranged in accordance with the theoretical data of Figure 1;

Figure 3 is a perspective view to an enlarged scale of a mounting arrangement for rollers such as those shown'in Figure 2;

Figure 4 is a view similar to Figure 2, but including'an arrangement for imparting stretch to the yarn beforeit is heated;

Figure 5 is a fragmentary view in vertical section of another type of arrangement for stretching and curling;

Figure 6 is a fragmentary perspective view of the apparatus of Figure 5;

Figure 7 is a view similar to Figure 1 but showing an alternative arrangement of the hyperboloids in relation-to the yarn path; and

Figure 8 is a view similar to Figure 1 but illustrating the positioning of the small diameter cooling arrangement that may be used in the assembly of the present invention.

In Figure l a hyperboloid 1 is shown. Such a body of revolution is obtained by revolving a straight line 2 around an axis 3 crossing the line 2 at an angle a. In Figure 1 angle oz is indicated by a line 4 parallel to the axis 3 which line 4 intersects the straight generatrix line 2 of the hyperboloid 1 in its middle.

If a second hyperboloid 5 having an axis 6 is laid against the first mentioned hyperboloid 1 in such a manner that the axes 3 and 6 of the hyperboloids 1 and 5 cross each other at an angle 2a, said two hyperboloids contact each other along a straight line which crosses the axis 3 of the hyperboloid 1 as well as the axis 6 of the hyper- Said latter angle is indicated in the same manner as the crossing angle between the line 2 and the axis 3 of the hyperboloid 1. In Figure 1 said straight line is identical with line 2 and therefore indicated with the same reference number.

With the foregoing description of the geometry of their curvature the rollers of Figure 2 will be described. In the device according to Figure 2 a pair of rollers 7 and 8, each of which has a peripheral surface in the form of 'a hyperboloid and will hereafter be called hyperboloidsfor short, are so placed opposite each other that the axes cross each other at an angle 20c.

'not shown. The hyperboloids 7 ands are rotated at the same speed and in opposite directions as shownby the arrows in Figure 2. The surface of the hyperboloids .7 and 8 is of an abrasion resistanttype of rubber.

Between the two hyperboloids 7 and 8 a thread '15:.is supplied at a constant speed from a supply package, not shown, by means of delivery rollers 16 driven at a constant speed by means of a motor, not shown, so that the tension between said supply device and the hyperboloid is controlled. From the delivery rollers 16, the yarn is guided to and through a tube 17 heated with electric resistance elements and connected to a source of electric current, not shown, through conductors 118 and 19. After passage of the yarn through the tube 17,

the thread goes through an air zone where cooling takes place and then passes between the hyperboloids 7 and 8. The rotating movement of the hyperboloids 7 and -8 pulls the thread 15 through the heating tube 17. Moreover, these rollers put twist in the thread between the delivery rollers 16 which acts as a twist stop at one end of the system and the point at which the thread comes into contact with the rollers. The twist is fixed by the action of the cooling air between the exit end of the tube 17 and the hyperboloids 7 and 8. In the illustrated embodiment the hyperboloids are rotated in a directionto produce Z-twist. If they were arranged in a position which would be a mirror image of the one shown, a false S-twist would be applied rather than a Z-twist. After leaving the hyperboloids 7 and 8, the thread 15 is wrapped around a godet type discharge roller 20 with an auxiliary roller 21. A twist leaves the thread between the hyperboloids 7 and 8 and the take up 20-21 but the curl has been permanently set by the heating and cooling. After leaving the take up 20-21, the yarn is led to a collecting device of any desired type, not shown. Twist in the same or in the opposite direction to the bias put in by the false twister may be put in at collection. 1

To curl eg a thread from polycaprolactam with a titre of 30 denier and 10 filaments, the hyperboloids 7 and 8 which have in the middle a diameter of 4.2 cm. and further a crossing angle on of 42 are rotated at 670 r.p.m. The supply speed of the thread must then be 60 m./min. whilst the temperature of the tube 17 with a length of 30 cm. must be maintained between 160 and 170 C. The air zone after the heating tube has a length of 40 cm. The discharge speed amounts to 68 m./min. The latter is so adjusted that before and after the hyperboloids the tensions in the thread are about the same. The threads so treated have a permanent bias to curl.

With the device described not only threads from polyamides but also threads consisting of other thermoplastic substances may be permanently curled.

Referring now to Figure 3, there are shown two hyperboloids 7' and 8'. The hyperboloid 7' is supported with its axis 22 in fixed bearings 23 and 24. On the other hand, the axis or supporting shaft 25 for the hyperboloid 8 is mounted in the arms of a fork-shaped carrier 26. This carrier is rotatably mounted on a shaft 27. The fork is biased to clockwise movement about the shaft 27 as it is viewed in Figure 3 by an adjustable counterweight 28 supported on a rod 29 and held in the position of adjustment by a set screw 30. The movements of the fork are damped by a paddle 31 immersed in an oil bath in a container 32. The paddle is connected to the fork by a shaft 33. In the embodiments of the invention shown in Figure 3, the pressure at which the two hyperboloids engage one another is dependent upon the position of the counterweight 28. Dancing is stopped by the paddle 31 in container 32. The drivmg arrangement for the hyperboloids is known and, therefore, need not be further described herein.

The arrangement of Figure 3 is particularly suitable for handling yarns of low denier. It will be appreciated that the rollers must not press together with too much force but the grip must be firm. With yarn of high denier, the arrangement of Figure 1 is quite satisfactory since the cross section of the yarn, particularly with rollers of rubber surface, is adequate to bring about the desired frictional drive. Notice that the hyperboloids 7 and 8 and 7 and 8' are completely identical in shape. This is of advantage in establishing the driving arrangements.

To obtain the maximum allowable twist in the yarns it is necessary to use hyperboloids of which the crossing angle between the axis and the generatrix lies between 40 and 45. With hyperboloids of said shape a twist may be laid in the threads the angle of pitch thereof lying between 50 and 45 and being always the complement of the crossing angle regardless of the thread thickness.

In case a smaller false twist is desired in the threads hyperboloids with a smaller crossing angle should be used. Thus only a kind of rolling together action is obtained if the crossing angle is chosen smaller than about 15 Such a device or a number of said devices in succession may be used in this manner to compress a cableshaped thread bundle or a fibre sliver. When applying more of said devices in succession the successive devices may be the mirror image of each other with regard to the arrangement of the hyperboloids.

Prior to the present invention, pre-stretched yarns were used as the starting material in the manufacture of curled yarn and it was believed, before this invention, that an increased tension during or after curling would reduce the crimping effect. It has now been found that an increase of the tension in the yarns during crimping causes the crimp to be more stable and uniform. An added advantage is the improved efiiciency of crimping and stretching as part of a single continuous operation.

Accordingly, in Figure 4 there is shown an arrangement where the yarn 34 is delivered by rollers 35 to and .around a stretch bar or rod 36, between the meshing teeth of'gear or cog wheels 37, through tubular heater 38 and between hyperboloids 39 and 40, corresponding respectively to hyperboloids 7 and 8 of Figure 2. From the hyperboloids 39 and 40, the yarn 34 is drawn off by a device 41 in all respects similar to the draw-off device 2021 of Figure 2. The hyperboloids 39 and 40 are mounted, made and located as previously described in Figure 2. Their surface may be made, as in the case of Figure 2, of an abrasion resistant natural or synthetic rubber. The stretching rod or bar 36 is disposed at a slight angle to the horizontal.

It is apparent that, in the arrangement of Figure 4, stretching occurs around the draw bar and in the yarn path between the delivery rollers 35 and the hyperboloids 39 and 40, the latter and draw off device 41 being driven at a higher velocity than the delivery rate of the rollers 35. Thus, stretching takes place immediately precedent to the false twisting which occurs between the meshing teeth of wheels 37 and the draw off device 41, the twist going in between the toothed wheels 37 and the hyperboloids 39 and 40 and coming out between hyperboloids 39 and 40 and the draw off device 41.

For instance, in order to stretch and to crimp a thread made from caprolactam with a titre of 30 denier and consisting of 10 filaments, the hyperboloids having in the middle a diameter of 4.2 cm. and further having a crossing angle of 42, are brought to rotate at 970 r.p.m. The supplying velocity of the thread should then amount to 35.5 m./min., whereas the temperature of the heater 38 measuring 30 cm. in length should be maintained at between and C.

The air zone after the tube measures 40 cm. in length. The velocity of the discharge device amounts to 106 m./min. The various velocities are so adjusted, that the thread tensions before and after engaging the hyperboloids approximately equal each other. The stretching of the thread takes place on the stretching rod 36, whereas the false twist in the thread runs back from the false twisting device comprising the hyperboloids to the small cog wheels 37 which serve as a twisting stop.

Instead of a. single stretching rod a stretching device 'known per se, comprising two or more rods, may also hyperboloid and its generatrix.

pipewhere itprojects beyond the base 42 and, on these hearings, there is mounted a sleeve 46, the outer surface of which functions as a pulley. A flange 47 is provided at the upper endof the pulley sleeve 46 and this flange has a central hole at 48 registering vertically with the hole in the pipe 43. A standard 49 projects upwardly from a margin of the flange 47 and, at the upper end of this standard, there is an overhanging piece provided with an eyelet 50 spaced from but in vertical registry with the opening at 48. Mounted on the standard 49 there is a yarn pulley 51 which is mounted on a shaft 52 by ball bearings 53 so that the pulley 51 is very freely rotatable about its supporting shaft.

When a belt is applied to the surface of the pulley sleeve 46, the pulley sleeve 46 is rotated about the yarn path as an axis and the pulley 51 rotates also about that path which is normal to its own axis. The construction of Figures and 6 can be substituted for the hyperboloids in the assembly of Figure 4. The rotation of the pulley sleeve 46 imparts twist between the point of delivery of the yarn and the pulley 51. In this case the twist is, of course, brought about by the rotation of the pulley sleeve 46 but since the pulley 51 is freely rotatable, the stretch is brought about by running the draw oif device '41 at a peripheral speed desirably in excess of the delivery rollers 35. It is to be noted that the wrap of the yarn around pulley 51 exceeds 360. The threading is likewise quite apparent from Figures 5 and 6, the yarn passing through the pipe 43 and the orifices 48 and 50'.

It will be observed that the arrangement of Figure 7 is identical to that shown in Figure 2 except for the angulardisposition of the hyperboloids. In Figure 7, the feed rollers are designated by numeral 54, the heater by 55, the hyperboloids as 56 and 57, respectively, and the take up device as 58.

In Figure 7, the hyperboloids 56 and 57 are identical to the hyperboloids shown in Figures 2 and 4. They are arranged in the same angular disposition to one another, that is the angle defined between their axis is equal to twice a where a is the. angle between the axis of the On the other hand, in Figure 7 the hyperboloids are differently located in rel-ation to the thread path, for in Figure 7 they are located sothat the yarn bisectsthe angle 20; rather than the angle 180' 2a. Two hyperboloids touching one another and driven at the same angular velocity with regard to each other move with equal velocities in corresponding points on the line of mutual contact. However, the directions of movement of the two hyperboloids are not the same at any given point of contact but form an angle with respect to one another. A thread pinched between said pair of hyperboloids is therefore not only twisted but propelled. As a result of this a twist which is always equal is imparted to the yarn between the thread supplying device such as the rollers 54 and the hyperboloids 56 and 57.

In the case of Figure 7, the twist produced is higher than that which is obtained by leading the thread between the hyperboloids perpendicular to their mutual lines of contact. In order to achieve this result, however, it is highly important that the hyperboloids be surfaced with material that will be of high co-efiicient friction. With the angular disposition of the hyperboloid pair in relation to the yarn path, which is depicted in Figure 7, it is likewise possible to use the general mounting arrangement disclosed in Figure 3.

In Figure 8, reference numeral 59 represents the feeding rollers, 60 represents the heating tube, 61 and 62 represent the hyperboloids and 63 represents the take up device. Instead of using air cooling, however, as is contemplated in the arrangements of Figures 2 and 4, the arrangement of Figure 8 contemplates the use of a cooler in which there is a small tube 64 of a diameter only very slightly exceeding the diameter of the thread and presenting a smooth, uniform heat absorbing surface.

This tube is surrounded by brine or other cold refrigerant chamber 65 that is supplied with circulating refrigerant through tubes 66 and 67. According to the arrangement of Figure 8, it is possible to conduct crimping operations at a velocity exceeding meters a minute. The internal diameter of the heating tube 60 exceeds the diameter of the yarns to such a little extent that the yarn, because of its oscillation incident to propulsion, contacts the inner wall of the heater with good uniformity as described in commonly owned copending application Serial No. 563,852, filed January 30, 1956. The length of the heating tube is 6 cm. for each 10 meters of thread velocity. If the cooling tube 64 is maintained at 20 C. or less the length of it may be about 2 cms. for each 10 meters of yarn velocity. In curling polycaprolactam yarns the tube 60 is kept at 160 to 175 C.

As an example of the operation of Figure 8, a thread made from polycaprolactam of 30 denier and 10 filaments was delivered at a velocity of meters 9. minute. In this case, the hyperboloids 61 and 62 had a diameter of 4.2 cms. in the center and a crossing angle of 42. They were rotated at 958 r.p.m. The heating tube 60 was 50 cms. long and was held at a temperature of to C. The cooling tube was 20 cms. and was held at 15 C. by circulating a cooling liquid therethrough countercurrent to the thread, see the arrows in Figure 8. The resulting yarn was found to be quite comparable in quality to a similar one which had been air cooled while moving through apertures such as that shown in Figure 2 at only 40 meters a minute. 7

The small tube 64 may be replaced by a helical wound tube through which a cooling medium is delivered, the diameter of the core of the helix being not inexcess of one meter. A metal block may be used as a cooling device it being provided with a bore of 1 mm. and having a parallel bore through which the coolant is circulated. Slits for the lateral entry of the yarn as described in commonly owned application Serial No. 563,852, filed January 30, 1956, may be applied not only to the heating tube 60, but also to the cooling tube 64. Air cooling of the tube 64 is possible if it is provided With radiation fins or other cooling surface enlarging media.

What is claimed is: 1. Apparatus for curling thermoplastic yarns that comprises yarn draw 01f means, yarn delivery means, heating means in the yarn path between said delivery and draw oif means, and a pair of driven rollers in the yarn path between said heating means and said draw ofi means, said rollers being in the form of hyperboloids disposed in mutual surface contact with their axes crossing at an angle equal to twice the angle between the hyperboloid axis and the line constituting its generatrix.

2. Apparatus for curling thermoplastic yarns that comprises yarn draw oflf means, yarn delivery means, heating means in the yarn path between said delivery and draw oif means, a pair of rollers in the form of hyperboloids disposed in mutual surface contact with their axes crossing at an angle equal to twice the angle between the hyperboloid axis and the line constituting its generatrix, and means for supporting said rollers in a position such that the yarn path between the heating means and the draw off bisects two of the angles resulting from the crossing of the axes of the hyperboloids.

3. Apparatus for curling thermoplastic yarns that com-- prises yarn draw olf means, yarn delivery means, heating means in the yarn path between said delivery and draw off means, a pair of rollers in the form of hyperboloids disposed in mutual surface contact with their axes crossing at an angle equal to twice the angle between the hyperboloid axis and the line constituting its genera-- trix, and means for supporting said rollers in a position such that the yarn path between said heating means and said draw oif means bisects said angle equal to twicethe angle between the axis of the hyperboloid and the line constituting its generatrix.

1 ..4. Apparatus for curling thermoplastic yarns that com- .prisesfyarn draw off means, roller means for delivering 'yarn to'said draw 01f means, a twist stop inthe yarn path between said means, a false twister in the yarn path between said stop and said drawofl means, yarn heating means in the yarn path between said stop and said false twisting means, a stretch bar in the yarn path between the said delivery means and said stop, and means for driving said draw E means faster than said delivery means whereby'succeeding lengths of running yam may be stretched, heated andcurled in continuous fashion.

5. Curling apparatus as claimed in claim 2 in which the angle between the axisof the hyperboloid and the 'line constituting its generatrix is between 40 and 45 degrees. i

6. Apparatus for curling thermoplastic yarns that comprises yarn draw as means, yarn delivery means, heating means in theyarn path between the said delivery and draw off means, a pair of rollers, said rollers being in the form of hyperboloids disposed in mutual surface contact with their axes crossing at an angle equal to twice the angle between the axis of the individual hyperboloid and the line constituting its generatrix, means mounting one of said rollers in fixed position, means mounting the other of said rollers for rocking move ment toward and away from the [first said roller, and a counterweight biasing said movable roller against the first said roller. '7. Apparatus for curling thermoplastic yarns that comprises yarn draw off means, yarn delivery means, heating means in the yarn path between said delivery and draw off means, a pair of rollers, said rollers being in the form of hyperboloids disposed in mutual surface contact with their axes crossing at an angle equal to twice the angle between the axis of the hyperboloid and the line constituting its generatrix, means for supporting said rollers with two opposite angles defined by their crossing bisected by the yarn path, means for independently rotating said rollers, a tube surrounding the yarn path between said heater and said rollers, said tube being of a diameter only slightly in excess of that of the yarn being curled, and means to circulate a coolant in heat exchange relationship to said tube.

8. Apparatus for curling thermoplastic yarns that comprises yarn draw off means, yarn delivery means, heating means in the yarn path between'said delivery and said draw ofi means, a pair of rollers, said rollers being in the form of hyperboloids disposed in mutual surface contact with their axes crossing at an angle equal to twice the angle between the axis of the hyperboloid and the line constituting its generatrix, means for supporting said rollers with two opposite angles defined by their crossing bisected by the yarn path, means for independently rotating said rollers, a tube surrounding the yarn .path between said heater and said rollers, said tube being of a diameter only slightly in excess of that of the yarn being curled, and means to circulate a coolant in heat exchange relationship to said tube and countercurrent to the direction of yarn movement around the exterior of said tube.

' r 9. Apparatus for curling thermoplastic yarns that comprises yarn draw ofl? means driven at a first speed, yarn delivery means driven at a second reduced speed, a twist stop in the yarn path between said draw oil and delivery means, a pair of driven rollers in the yarn path between said stop and draw off means, said rollers being in the form of hyperboloids disposed in mutual surface contact with their axes crossing at an angle equal to twice the angle between the hyperboloid axis and the line constituting its generatrix, yarn heating means in the yarn path between said stop and said rollers, and a stretch bar in the yarn path between said delivery means and said stop, whereby succeeding lengths of running yarn may be tensioned, heated and curled in continuous fashion.

References Cited in the file of this patent UNITED STATES PATENTS 

